Despite widespread concern over heated diplomatic debates and growing interest in public diplomacy, it is still incompletely understood what type of message is more effective for gaining support from foreign public, or the international society, in situations where disputing countries compete in diplomatic campaigns. This study, through multiple survey experiments, uncovers the effect of being silent, issuing positive justification, and negative accusation, in interaction with the opponent’s strategy. We demonstrate that negative verbal attacks “work” and undermine the target’s popularity as they do in electoral campaigns. Unlike domestic electoral campaigns, however, negative diplomacy has little “backlash” and persuades people to support the attacker. Consequently, mutual verbal fights make neither party more popular than the other. Nevertheless, this does not discourage disputants from waging verbal fights due to the structure similar to the one-shot prisoner’s dilemma. We also find that positive messages are highly context-dependent—that is, their effects greatly depend on the opponent’s strategy and value proximity between the messenger and the receiver.